4 2 quantum theory
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4-2 Quantum Theory. Planck’s Theory. Max Planck predicted accurately how the spectrum of radiation emitted by an object changes with temperature. Proposed that there is a fundamental restriction on the amounts of energy that an object emits or absorbs, called quantum. Means FIXED AMOUNTS.

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4-2 Quantum Theory

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4 2 quantum theory

4-2 Quantum Theory


Planck s theory

Planck’s Theory

  • Max Planck predicted accurately how the spectrum of radiation emitted by an object changes with temperature.


4 2 quantum theory

  • Proposed that there is a fundamental restriction on the amounts of energy that an object emits or absorbs, called quantum.

    • Means FIXED AMOUNTS


4 2 quantum theory

  • Completely contradicted the idea that energy can emit or absorb in any amount.

  • Related the Frequency of the radiation to the amount of energy.

  • E = h

  • Energy = Planck’s Constant x Frequency


4 2 quantum theory

  • Planck’s Constant (h) = 6.6262 x 10-34 J-s (Joule x second)

  • Energies absorbed or emitted by atoms are quantized, which means that their values are restricted to certain quantities. Energy is not continuous


Example

Example

  • Imagine a car’s fundamental quantum of energy corresponds to a speed of 10 km/hr. If the car has 7 quanta of energy, it will have a speed of 70 km/hr. If the car has 9 quanta of energy, it will have a speed of 90 km/hr. This shows that a car can only move in multiples of 10 km/hr (in this case). Speeds such as 88 km/hr and 41 km/hr are impossible


4 2 quantum theory

  • QuantizedContinuous


4 2 quantum theory

  • Why can’t we see quantized energy around us?

    • Planck’s Constant is very small. The Quanta are too small for every day notice, but to a very small atom they make a big difference


The photoelectric effect

The Photoelectric Effect

  • In the photoelectric effect, electrons are ejected from the surface of a metal when light shines on it.

  • Einstein realized that Planck’s idea of energy quanta could explain this.

  • Said that Light consists of quanta of energy that behave like tiny particles, called PHOTONS


4 2 quantum theory

  • Red light will not cause electrons to flow in a sheet of sodium metal, no matter how long or bright the source is. Violet light will cause electrons to flow. Violet light has a greater frequency, and a greater amount of energy per photon


4 2 quantum theory

  • The frequency of light and the energy of the photon explains the effects of electromagnetic radiation.

  • X-rays contain high amounts of energy because of their frequency, while radio waves have low frequency and low energy.


Dual nature of radiant energy

Dual Nature of Radiant Energy

  • Arthur Compton later demonstrated that photons can collide with electrons.

  • Photons behave like a particle that always travels at the speed of light.

  • E = mc2 =h


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